A low cost cation exchange membrane to be used in a specific bioelectrochemical system has been developed using poly(ether ether ketone) (PEEK). This material is presented as an alternative to current commercial ion exchange membranes that have been primarily designed for fuel cell applications. To increase the hydrophilicity and ion transport of the PEEK material, charged groups are introduced through sulfonation. The effect of sulfonation and casting conditions on membrane performance has been systematically determined by producing a series of membranes synthesized over an array of reaction and casting conditions. Optimal reaction and casting conditions for producing SPEEK ion exchange membranes with appropriate performance characteristics have been established by this uniquely systematic experimental series. Membrane materials were characterized by ion exchange capacity, water uptake, swelling, potential difference and NMR analysis. Testing this extensive membranes series established that the most appropriate sulfonation conditions were 60 °C for 6 h. For mechanical stability and ease of handling, SPEEK membranes cast from solvent casting concentrations of 15%–25% with a resulting thickness of 30–50 µm were also found to be most suitable from the series of tested casting conditions. Drying conditions did not have any apparent impact on the measured parameters in this study. The conductivity of SPEEK membranes was found to be in the range of 10⁻³ S cm⁻¹, which is suitable for use as a low cost membrane in the intended bioelectrochemical systems.

Membranes with high solvent permeance and excellent molecular sieving characteristics are highly desirable for energy-efficient organic liquid separation. However, the “trade-off” relationship between permeability and solute selectivity remains a challenge for thin film composite (TFC) polymeric membranes. Herein, we report a facile and scalable fabrication technique for a high performance and solvent-resistant TFC membrane based on a nanofibrous hydrogel network. Aramid nanofibers (ANF) with a diameter of ∼12.3 nm were used to construct a three-dimensional interconnected hydrogel structure and to obtain a homogeneous diffusion of the aqueous solution. A polyamide (PA) nanofilm with a thickness down to 62 nm was successfully fabricated on the nanofibrous hydrogel support via controlled interfacial polymerization (IP) and was found to have an unprecedented solvent permeation for mild polar solvents (methanol: 54.0 L m⁻² h⁻¹ bar⁻¹) and aggressive organic solvents (acetone: 70.0 L m⁻² h⁻¹ bar⁻¹, dimethyl formamide: 34.0 L m⁻² h⁻¹ bar⁻¹). These permeabilities are over two orders of magnitude higher than those of commercial membranes, with a similar selectivity. The ease of preparation stimulates industrial scale-up and opens up future possibilities for applications in molecular separation, solvent recovery, water treatment and water desalination.

Biofouling is a major challenge in the water industry and public health. Silver nanoparticles (AgNPs) have excellent antimicrobial properties and are considered to be a promising anti-biofouling agent. A modified method was used to produce small sized and well-dispersed biogenic silver nanoparticles with a mean size of ~6 nm (Bio-Ag0-6) using Lactobacillus fermentum. The morphology, size distribution, zeta potential and oxidation state of the silver were systematically characterized. Determination of minimal inhibitory and bactericidal concentration results revealed that biogenic silver Bio-Ag^0-6 can effectively suppress the growth of the test bacteria. Additionally, the inhibition effects of Bio-Ag^0-6 on biofilm formation and on established biofilms were evaluated using P. aeruginosa (ATCC 27853) as the model bacterium. The results from microtiter plates and confocal laser scanning microscopy demonstrated that Bio-Ag^0-6 not only exhibited excellent antibacterial performance but also could control biofilm formation and induce detachment of the bulk of P. aeruginosa biofilms leaving a small residual matrix.

To improve the filtration performance and antifouling properties of ultrafiltration (UF) membranes, novel polymer blend UF membranes were fabricated in this study. Carboxylic acid functionalized polysulfone (PSFNA) was synthesized by modifying polysulfone (PSF) with 6-hydroxy-2-naphthoic acid (HNA). A series of polymer blend UF membranes were fabricated by adding different amounts of PSFNA into polyethersulfone (PES) to form a homogeneous casting solution. The influences of PSFNA on the morphology, thermal stability, hydrophilicity, filtration performance and antifouling properties of the blend membranes were investigated. The results indicated that by adding PSFNA into PES membranes, the finger-like pores in the membranes became larger, and the porosity and surface hydrophilicity of the membranes were improved. Compared with the pristine PES membrane, PES/PSFNA membranes demonstrated improved filtration performance, resulting in both increased water flux and higher bovine serum albumin (BSA) rejection. At a feed pressure of 0.1 MPa, the PES/PSFNA membrane with 4.0 wt% PSFNA had a pure water flux of 478 L m⁻² h⁻¹, which was 1.7 times higher compared with the PES membrane (287 L m⁻² h⁻¹). In addition, the antifouling properties of PES membranes were also enhanced with the addition of PSFNA. The PES/PSFNA membranes with 3.0 wt% PSFNA had a total fouling ratio (TFR) of 49.6%, as compared with 62.5% for PES membranes.